1. Field of the Invention
The present invention relates to a magnetic tape cartridge which is operable with a Leader block and leader block pin, the leader block and leader block pin being uniquely configured so as to be inoperable with a prior art leader block and leader block pin.
2. Discussion of the Related Art
IBM developed the 3480/3490 type magnetic tape cartridge which is processed by the 3480 or 3490 type cartridge drive. This type of magnetic tape cartridge has a leader block which recesses and nests in one of the corners of the cartridge. The leader block is connected to a leader of the magnetic tape which is stored on a reel within the cartridge. The leader block is notched to provide a cavity for receiving and interlocking with an enlarged portion of a pin associated with the cartridge drive. The pin is connected to an arm which is operated by the cartridge drive for pulling the leader block out of the cartridge and threading the magnetic tape onto a reel for processing purposes, such as read/write functions. The 3480/3490 magnetic tape cartridge and cartridge drive are commercial items in the industry. The magnetic tape is formulated with chromium dioxide and has a thickness of about 72 gauge. The 3480/3490 cartridge drive is designed to process tapes with these characteristics.
The industry has seen the emergence of a new magnetic tape which is significantly different from the former magnetic tape. The new magnetic tape has a formulation of metal particles and has a reduced thickness, namely about 57 gauge. It is necessary that a new tape drive be provided which can process the new tape with less tension than that applied to the existing tape. Further, the new drive must be able to process the new formulation of the tape. Except for these modifications, it is desired that the new tape drive be substantially the same as the existing tape drive. With this arrangement the existing tape drives can be converted to new tape drives with minor modifications. This protects the significant investment that has been made in the existing tape drives. It is important that the new magnetic tape cartridge not be inserted into the existing tape drives or that the existing magnetic tape cartridge not be inserted into the new tape drive. If either one of these occurrences took place, it would most likely result in destruction of the tape and loss of important data. In order to solve this problem, efforts have been undertaken to electronically detect insertion of an improper cartridge. This approach, however, required the tape to be threaded into the drive before preventative measures were undertaken. It is desirable that this problem be solved before the magnetic tape is moved into the cartridge drive by an arrangement which does not require electronic sensing devices.